JPH0974053A - Electrical double-layer capacitor electrode and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a forming electrode without using any binder by heating a resin material within an atmosphere within a specific pressure range, at a melting temperature or higher of the resin, and at a temperature or lower where oxidation reaction starts for tentative baking. SOLUTION: Resin, PVDC, which becomes a raw material is heated at 200-500 deg.C which is equal to or more than the temperature of a heat-absorbing ending point due to a melt point or fusion and at the temperature or less of oxidation reaction point to obtain a tentatively baked resin. Then, the tentatively baked resin is cooled to normal temperatures and is ground by a vibration mill or a roll mill and then a powder tentatively baked resin is boiled in water. Then, the powder tentatively baked resin is subjected to pressurization tentative formation in an atmosphere of a pressure range of 0.01-10kg/cm<2> and is heated and baked at a temperature above the exidation reaction point, namely 500-900 deg.C, to obtain a porous carbon forming body. Therefore, since baking is performed while leaving a proper amount of volatile constituent in a material, a forming electrode can be manufactured without using any binder, thus obtaining a large-capacity capacitor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for an electric double layer capacitor and a manufacturing method thereof, and more particularly to an electrode for an electric double layer capacitor most suitable for obtaining a large capacitance and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, charge accumulation based on electric double layers,
That is, an electric double layer capacitor using the electric double layer principle has been developed and commercialized. Since the capacitor can obtain a large electrostatic capacity, a small capacitor can be used as a backup power source for a semiconductor memory of an electronic device, and a large capacitor. Are used for some of the applications of lead batteries in vehicles.

As an electrode material for this type of electric double layer capacitor, powdered activated carbon was obtained in the first step of pressurizing carbon powder mixed with water at a pressure of 50 kg / cm 2 while heating at about 700 ° C. Temperature of 700-1000 ℃ 50-8
A method for producing a molded body of activated carbon from the second step of pressure molding at a pressure of 00 kg / cm 2 is disclosed in Japanese Patent Application Laid-Open No. 3-201520, which is a patent document filed by the present applicant.

As a result of earnest research and development on electrodes for electric double layer capacitors, the present applicant heated polyvinylidene chloride resin in a non-oxidizing atmosphere, thereby causing atomic and molecular defects to generate pores. We have developed an electrode material that has been formed with, and filed a patent application (Patent Application 6
-67827). This material is a porous carbon material having extremely fine pores and has a higher capacity than that of conventional activated carbon.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the molding method disclosed in No. 1520, since carbon powder is used as a starting material, volatile components that contribute to solidification evaporate in the process of carbonization and solidification is difficult, and a large amount of power or energy is required for molding. Since there is a problem that the manufacturing cost is high and the molding density cannot be increased because a binder is used to help solidify the carbon powder, the electric capacity decreases by the amount of the binder when used as a capacitor. I will end up. If the resin, which is a raw material of carbon, is crushed and molded as it is and then sintered, the amount of volatile components is too large to maintain the shape. This is because a large amount of volatile components evaporate during firing, and the evaporating force causes the shape to collapse. That is, in the conventional method, the carbon powder could not be sufficiently solidified because the volatile component was too much or too little, or the amount was not appropriate.

[0006]

In order to solve the above-mentioned problems and to reduce the manufacturing cost, the present invention uses a resin as a starting material, and uses the resin in a pressure range of 0.01 to 10.
Manufacture a calcined resin by heating in an atmosphere of kg / cm2 and above the melting point of the resin, or above the temperature at which the endothermic reaction due to melting (softening flow) of the resin ends and below the temperature at which the oxidation reaction begins And the step of cooling the calcined resin to room temperature to make powder, and manufacturing the calcined powder resin, and after press-molding the calcined powder resin, heating at a temperature above the temperature at which the oxidation reaction of the resin starts. Or a step of heating the calcined powder resin at a temperature not lower than the temperature at which the oxidation reaction starts to obtain a molded carbon body, the method for producing an electric double layer capacitor electrode.
Furthermore, the present invention relates to an electrode of an electric double layer capacitor obtained by carbonizing a resin, wherein the electrode has a pore diameter of 20 angstroms or more, and the proportion of the pores of the electrode in the total surface area is 10% or less. A featured electric double layer capacitor electrode is provided. Further, in the case of a thermoplastic resin containing halogen or a thermoplastic resin not containing halogen as the resin, halogen is added by an appropriate method at an appropriate time in the production process, and an electrode for an electric double layer capacitor is produced. A method is provided.

[0007]

As described above, according to the present invention, the resin material is placed in an atmosphere having a pressure range of 0.01 to 10 kg / cm @ 2 and at a melting point temperature of the resin or higher, or the resin is melted (softened and fluidized). ), The temperature is above the temperature at which the endothermic reaction ends and below the temperature at which the oxidation reaction starts, and calcining is performed with the appropriate amount of volatile components in the material remaining, so a binder is used. Without doing so, a molded electrode can be manufactured, and a capacitor with a larger capacity can be provided.

[0008]

EXAMPLES The inventor of the present invention focuses on the fact that the mass change is due to the evaporation of volatile components in the resin in order to invent a method for producing a porous charcoal compact which is optimal as an electrode of an electric double layer capacitor. Then, using a powdery polyvinylidene chloride resin (PVDC) suitable for producing porous carbon, the characteristics of mass change and reaction heat during heating are investigated, and heating temperature during heating and evaporation of volatile components By grasping the relationship with the amount, we obtained the heating temperature at which the volatile components effective for molding remain. 12 and 13 are diagrams showing the results, and in these diagrams, the horizontal axis shows the heating time and the vertical axis shows the mass and temperature. FIG. 12 shows the characteristics when PVDC is heated in an oxidizing atmosphere (air), and FIG. 13 shows the characteristics when heated in a non-oxidizing atmosphere (nitrogen gas). The curve a in these figures is raised at a heating temperature of the heating furnace in proportion to the time axis, and the change in mass (curve b) and reaction heat characteristics (curve c) at that time.
Is shown.

First, when the reaction heat (curve c) of FIG. 12 is heated when heated in an oxidizing atmosphere (air), c
Reaction heat is decreasing at 1 point. This is due to the endothermic reaction due to melting, and it was found that this point is the melting point of this resin and there is almost no change in mass at this point, that is, the volatile components in the resin have hardly evaporated. This endothermic reaction was completed at point c2, and it was found that mass reduction (evaporation of volatile components in the resin) was rapidly occurring at this point. By the way, in the case of PVDC, which was tested this time,
The melting point was 175 ° C., and the end point of the endothermic reaction due to melting was 230 ° C. The same phenomenon occurs at points c1 and c2 above when heated in a non-oxidizing atmosphere. From this, it can be said that the reaction of c1 and c2 is not a reaction involving oxidation, that is, combustion.

When the heating is further advanced, when the heating is carried out in an oxidizing atmosphere (in the air), the reaction heat sharply rises at point c3 of the curve c in FIG. 12, but the heating is carried out in a non-oxidizing atmosphere. When it did, it turned out that this phenomenon did not occur. From these, it was found that the point c3 when heated in an oxidizing atmosphere (in the air) is a reaction due to oxidation. By the way, P
In the case of VDC, the c3 point was 530 ° C. From the above analysis results, it was found that in order to produce a molded body, a material having a volatile component that contributes to molding can be obtained by heating at a temperature of the c1 point or the c2 point or higher and a temperature of the c3 point or lower. .

Based on the above findings, the electrode of the electric double layer capacitor was manufactured by the manufacturing method shown in FIG. 1 as Example 1.
The capacitor performance was measured. FIG. 1 will be described. First, the resin as a raw material, PVDC, has the melting point (c
1 point) or end point of endotherm due to melting (c2 in FIG. 12)
Point) and a temperature not higher than the oxidation reaction point (point c3 in FIG. 12) at 250 to 300 ° C. for 30 minutes to obtain a calcined resin. Next, the calcined resin was cooled to room temperature and pulverized with a vibration mill, a roll mill or the like to obtain a powder calcined resin. This powdered resin was boiled in water. This boiling step may be omitted, but boiling was more effective for capacitor performance.
Next, the powder calcined resin is pressure-temporarily molded, and the temperature is 700 ° C. and 850 ° C. above the oxidation reaction point (c3 point in FIG. 12).
The mixture was heated and baked at 0 ° C. to obtain two types of porous carbon compacts. The temperature pattern of the above manufacturing method is shown in FIG. In FIG. 11, the holding time of the firing temperature is 1 to 15 minutes, but it may be 1 hour or less.

Next, as shown in FIG. 2 as a second embodiment,
A porous carbon molded body was obtained in the same manner as in Example 1 except that pressure pre-molding in Example 1 (FIG. 1) was not performed, and pressure / heat firing was performed to manufacture an electrode of an electric double layer capacitor. The capacitor performance was measured.

As shown in FIG. 3 as Example 3, in the first heating step for obtaining the calcined resin of Example 1 (FIG. 1) under a steam atmosphere, the pressure during heating is from no pressure to 20 kg / cm.
A porous carbon compact was obtained in the same manner as in Example 1 except that the electrolyte was boiled and impregnated after the second heat treatment and microwave treatment was performed, and the electrode of the electric double layer capacitor was applied. It was manufactured, and its pore size distribution and capacitor performance were measured.

FIG. 4 shows a process chart of the manufacturing method of the fourth embodiment. In this embodiment, the resin is a halogen-free thermoplastic polybutylene terephthalate (hereinafter referred to as PBT), and the manufacturing method is the first heating step for obtaining the calcined resin of Example 3 (FIG. 3). A porous carbon compact was obtained in the same manner as in Example 3 except that the pressure during heating was applied under a hydrogen atmosphere of 3 kg / cm @ 2, the electrode of the electric double layer capacitor was manufactured, and the capacitor performance was measured.

A process diagram of the manufacturing method of Example 5 is shown in FIG. In this example, the resin was PBT, and the manufacturing method was the same as in Example 3 (FIG. 3) except that a step of mixing PBT and an aqueous hydrochloric acid solution was added before the first heating step for obtaining the calcined resin. A porous carbon molded body was obtained in the same manner as in Example 3, an electrode of an electric double layer capacitor was manufactured, and the capacitor performance was measured.

For comparison, PVDC is 700-9.
What was carbonized in a non-oxidizing atmosphere at 00 ° C. was mixed with a binder (Teflon resin) and molded to obtain a porous carbon molded body, and similarly the capacitor performance was measured. Further, the distribution of pore diameters and the capacitor performance were measured for six types of commercially available activated carbon (represented by symbols A to F).

The experimental results of the electrostatic capacitance of the electric double layer capacitors having these electrodes are shown in FIG. Example 3 in FIG.
Regarding the results, the results of the case where the pressure during the first heating is unpressurized and the case where the pressure at which the electrostatic capacity is maximum is 3.0 kg / cm @ 2 are described. From the results shown in FIG. 6, it can be seen that Example 1 has the same performance as the Comparative Example without the binder and no pressure is applied during heating and firing, and Example 2 is compared by performing pressure and heating firing. A capacitance of 1.3 to 1.6 times that of the comparative example can be obtained. It was found that this would lead to a three-fold increase in capacity. When not using microwave, 2 in the atmosphere
It is known that the same result can be obtained by performing heat treatment at 00 ° C. for about 1 hour. Here, a microwave that can shorten the time is used. Furthermore, it was found that the capacities of Examples 4 and 5 were equivalent to those of Example 3. Although PBT was exemplified as the resin containing no halogen in Examples 4 and 5,
For polyethylene terephthalate and polycyclohexane terephthalate, electrodes of electric double layer capacitors were manufactured and the performance of the capacitors was measured.
It was possible to obtain the same performance as that of No. 5. Further, in Example 4, the pressurization / heat treatment was carried out in a hydrogen chloride atmosphere,
The same performance as in Example 4 was obtained even in a fluorine, bromine, or iodine atmosphere. Further, the same performance as in Example 5 could be obtained even when the solution mixed with the resin in Example 5 used an aqueous solution of fluorine, bromine, or iodine instead of the hydrochloric acid aqueous solution. Here, for comparison, in Example 4, a sample treated in a sulfuric acid atmosphere instead of a hydrogen chloride atmosphere and a sample in Example 5 mixed with dilute sulfuric acid instead of an aqueous hydrochloric acid solution were trial-produced, and electrodes of an electric double layer capacitor were prepared. Was manufactured and its capacitor performance was measured, and the capacitance was 20 to 40% lower than those of Examples 4 and 5. From the above, it is possible to use a halogen-containing thermoplastic resin as the raw material for the electrodes of electric double layer capacitors, or to add a halogen-free thermoplastic resin by adding halogen at an appropriate time and at an appropriate method in the manufacturing process. It has been found that an electrode having a large capacitance can be manufactured.

FIG. 7 shows the capacitance when the pressure applied in the first heating step was changed in Example 3, and FIG. 8 shows the capacitance with respect to the total surface area when the pressure applied in the first heating step was changed. Pore diameter 2
The ratio of the surface area of pores of 0 angstrom or more is shown.
From FIG. 7, it was found that when the applied pressure in the first heating step was changed, the electrostatic capacity showed the maximum at a pressure of 3.0 kg / cm2, and the minimum capacity at no pressure and at a pressure of 10 kg / cm2 or more. It was Further, when the pressure applied in the first heating step is changed from FIG. 8, the ratio of the surface area of pores having a pore diameter of 20 angstroms or more to the total surface area is 3.0 kg of pressure.
/ Cm2 shows the minimum, no pressure and pressure 10kg / cm
It was found that the ratio of the surface area of pores having a pore diameter of 20 angstroms or more to the total surface area was large when the ratio was 2 or more. By the way, the reason for paying attention to the surface area of pores having a diameter of 20 angstroms or more is 20
This is because it is generally practiced to use Angstrom as a boundary. For example, in 1972, IUPAC (In
ternational Unionof Pore and Applied Chemistry)
Macro pores: 500 Å or more, mesopores: 500 to 20 Å, micropores: 20 to
8 angstrom, sub-micropore: A classification of pores of 8 angstrom or less is defined.

FIG. 9 shows that the applied pressure in the first heating step of Example 3 was not applied, the pressure was 3.0 kg / cm 2, and the total surface area of seven types of commercially available activated carbons A to G. The capacitance and the ratio of the surface area of pores having a pore diameter of 20 Å or more are shown. FIG. 10 is a graph showing the data of FIG. 9, in which the horizontal axis represents the ratio of the surface area of pores having a pore diameter of 20 Å or more to the total surface area, and the vertical axis represents the capacitance. From these figures, the pore size to the total surface area is 2
The ratio of the surface area of pores of 0 angstrom or more is 10%
It was found below that the increase in capacitance was significant.

[0020]

As described above, according to the present invention, the resin material is kept in an atmosphere having a pressure range of 0.01 to 10 kg / cm @ 2, at a temperature above the melting point of the resin and below the temperature at which the oxidation reaction starts. By heating and calcining, firing is performed in a state where an appropriate amount of volatile components in the material remains, so that a molded electrode can be manufactured without using a binder, and a capacitor with a larger capacity is provided. be able to. When a high-performance electrode is required, the resin material should be in an atmosphere with a pressure range of 0.01 to 10 kg / cm2, and at a temperature higher than the temperature at which the endothermic reaction due to melting (softening flow) of the resin ends. It can be obtained by heating at a temperature not higher than the temperature at which the oxidation reaction starts and calcining, and simultaneously calcinating and heating and baking the calcined resin. As the above-mentioned resin material, a thermoplastic resin containing halogen is most suitable, but also for a thermoplastic resin containing no halogen, by adding halogen by an appropriate means, molding that exhibits the same performance as the resin containing halogen The electrodes can be manufactured.
The reason for setting the first heating temperature to "above the temperature at which the endothermic reaction accompanying the melting (softening flow) of the resin ends" is when heating below the temperature at which the resin melting ends, the pores inside the carbon It is because it is crushed and the surface area cannot be earned. Further, while the electrode formed by using the binder has a problem that the binder deteriorates, the electrode of the present invention does not have the drawback. Furthermore, by performing heat treatment in a steam atmosphere in the calcining step, the capacitance can be further improved.

[Brief description of drawings]

FIG. 1 is a process drawing showing a process for producing a porous carbon molded body according to Example 1 of the present invention.

FIG. 2 is a process drawing showing a process for producing a porous carbon compact according to Example 2 of the present invention.

FIG. 3 is a process drawing showing a process for producing a porous carbon molded body according to Example 3 of the present invention.

FIG. 4 is a process drawing showing a process for producing a porous carbon molded body of Example 4 of the present invention.

FIG. 5 is a process drawing showing a process for manufacturing a porous carbon molded body of Example 5 of the present invention.

FIG. 6 is a view showing one data in which the electrical performance of the porous carbon molded body of the example of the present invention was tested.

FIG. 7 shows a first porous carbon compact according to Example 3 of the present invention.
It is a figure showing the electrostatic capacity at the time of changing the pressurizing force of the heating process of.

FIG. 8 is a first porous carbon compact according to Example 3 of the present invention.
FIG. 6 is a diagram showing the ratio of the surface area of pores having a pore diameter of 20 Å or more to the total surface area when the pressure applied in the heating step is changed.

FIG. 9 shows a first porous carbon compact according to Example 3 of the present invention.
No pressure applied in the heating process, and pressure of 3.0 kg
/ Cm @ 2, and the ratio of the surface area of pores having a pore diameter of 20 angstroms or more to the total surface area of 7 types of commercially available activated carbons A to G, and the capacitance.

FIG. 10 is a graph showing the data of FIG.

FIG. 11 is a view showing a temperature pattern in the manufacturing process of the porous carbon molded body of the example of the present invention.

FIG. 12 is a graph showing the experimental results of the change in resin mass and the heat of reaction due to heating in the atmosphere.

FIG. 13 is a graph showing experimental results of resin mass change and reaction heat due to heating in nitrogen gas.

Claims (10)

[Claims] 1. A step of producing a calcined resin by using a resin as a raw material, heating the resin at a first heating temperature which is equal to or higher than a softening start temperature of the resin and is equal to or lower than a temperature at which an oxidation reaction starts,
A step of cooling the calcined resin to room temperature to form a powder, producing the calcined powder resin, a step of press-molding the calcined powder resin, and a second temperature above the temperature at which the oxidation reaction of the resin begins.
And a manufacturing step of obtaining a shaped carbon body by heating at a heating temperature of 1. The method for manufacturing an electric double layer capacitor electrode, comprising: 2. The first heating temperature is equal to or higher than a temperature at which an endothermic reaction associated with melting (softening flow) of the resin is completed and below a temperature at which an oxidation reaction is started. 1. The method for manufacturing the electric double layer capacitor electrode according to 1. 3. The production of an electric double layer capacitor electrode according to claim 1, wherein the step of producing the calcined resin is performed in an atmosphere having a pressure range of 0.01 to 10 kg / cm 2. Method. 4. The method for producing an electric double layer capacitor electrode according to claim 1, wherein the step of producing the calcined resin is performed in a steam atmosphere. 5. The first heating temperature is 200 ° C. to 500 ° C.
5. The method for producing an electric double layer capacitor electrode according to claim 1, wherein the temperature is at a temperature of ° C. 6. The second heating temperature is from 500.degree. C. to 900.
6. The method for producing an electric double layer capacitor electrode according to claim 1, wherein the temperature is at a temperature of ° C. 7. The method of manufacturing an electric double layer capacitor electrode according to claim 1, wherein the resin material is a thermoplastic resin containing halogen. 8. The method of manufacturing an electric double layer capacitor electrode according to claim 1, wherein the resin material is polyvinylidene chloride resin. 9. The resin material is a halogen-free thermoplastic resin, and halogen is added before the step of producing the calcined powder resin or during the step of producing the calcined powder resin. A method for manufacturing the electric double layer capacitor electrode according to claim 1. 10. An electrode of an electric double layer capacitor obtained by carbonizing a resin, wherein the ratio of pores having a pore diameter of 20 Å or more to the total surface area of the pores of the electrode is 1.
An electrode of an electric double layer capacitor, which is 0% or less.